Radio direction finder



1949- H. B. R. BOOSMAN ET AL 2,485,353

RADIO DIRECTION FINDER Filed May 1, 1946 Ana AMPLIFIER 2 werecm MIXER COMMON 7 VARIABLE PHASE SHIFFING DEVICE no LIFIEP MIXER LOCAL OSClLLATOR IZERIIMN BERMQRD .BOOSMAN flRISTIAANflNDEZUJSANETDELA 511510102125 INVENTORS.

AGENT Patented Oct. 18, 1 949 RADIO DIRECTION FINDER Herman Bernard Rudolf Boosman and Christiaan Jan de Lussanet de la Sabloniere, Eindhoven, Netherlands, assignors, by mesne assignments,

to Hartford National Bank and Trust Company, Hartford, Conn, as trustee Application May 1, 1946, Serial No. 666,248 In the Netherlands August 10, 1940 Section 1, Public Law 690, August s, 1946 Patent expires August 10, 1960 3 Claims.

This invention relates to a direction finder in which use is made of two uniform directional antenna systems which extend at right angles with respect to one another and are connected ode-ray tube there appears on the screen of the cathode-ray tube a line whose slope corresponds to the direction of the transmitter of which a bearing is taken. It is of importance that the amplification and the phase-displacement in the two receivers are exactly equal. Indeed, if the amplification in both channels were uneven the direction of the line on the screen would not tally with the course direction, whereas in the case of uneven phase-displacement an elliptical figure would ensue due to which correct reading of the course direction would be impeded.

The method by means of which it has hitherto been attempted to meet these conditions of even phase-displacement and amplification consists in that the receiver parts concerned are equalized as exactly as possible. It has appeared to be unfeasible sufficiently to reduce the deviation even over a narrow band of frequencies, whilst the construction of a direction finder according to the above-mentioned method was very expensive.

According to the invention it is possible to avoid errorsin the direction of a transmitter, of which a bearing is to be taken, independently of the wavelength of the oscillations emitted by the transmitter by providing a switch by means of which the input circuit of both receivers can be connected in parallel and by providing at least one of the receivers with a device by means of which both the phase displacement and the amplification factor can be controlled.

The invention will be more fully explained by reference to the accompanying drawing whose 'sole figure represents one form of construction of a direction finder according to the invention.

The sole figure represents two uniform frame antennas l and 2 which extend at right angles with respect to one another and are preferably connected to superheterodyne receivers 3 and 4 respectively. By giving the two superheterodyne receivers a common local oscillator I3 in a known manner, it is provided that not only in either case the intermediate frequencies are exactly equal, but, moreover, the phase-difference between the intermediate frequency voltages, generated by the two mixing tubes l1 and I8, respectively, is entirely equal to that between the two high frequency voltages that aresupplied to these tubes. The voltages set up in the output circuits of the receivers are supplied to an indicatin device. In the present form of construction the indicating device is a cathode-ray tube comprising two deflecting devices which extend at right angles with respect to one another. The voltages supplied by the receivers 3 and 4 are supplied to deflecting devices consisting of the pairs of plates 5, 5 and 6, 6 respectively as a result of which a straight line appears on the screen of the cathode-ray tube, the direction of the said line corresponding to the direction of the transmitter of which a bearing is taken, if the oscillations picked up by the antennas I and 2 respectively undergo the same amplification and phase-displacement in the transmitting circuits between antenna and deflecting device.

To attain this purpose a switch 1 is provided by means of which the input-circuits of the two receivers can be connected in parallel.

This switch may be constructed in various ways. For the sake of simplicity .a unipolar switch is shown in the drawing.

Furthermore the transmitting circuit comprises a device 9, provided between the antenna .2 and the pair of plates 6, 6, by means of which device the phase-displacement and the amplification of the said transmitting circuit can be controlled.

When the switch 1 is closed the same signs. is supplied to the input-circuits of the two receivers so that in the case of uniform phase displacement and amplification in both receivers, equal voltages are supplied to both pairs .of plates 5, 5 and 6, 6' of the cathode-ray tube. Consequently, a straight line forming an angle of 45 with the pairs of plates 5, 5' and 6, B will appear on the screen of the cathode-ray tube. If, in contradistinction thereto, the phase-displacement .in the two receivers is not uniform an elliptical figure ensues and in the case of uneven amplification of the two receivers the angle at which appears the stroke or the figure difiers from 45; in this way it can thus be ascertained whether the phase-displacement and the amplification of both receivers are equal to each other. If this is not the case the device 9 permits both the phase-displacement and the amplification factor of the receiver 4 to be adjusted until a straight line is obtained on the screen of the cathode-ray 3 tube which line forms an angle of 45 with the pairs of plates 5, 5' and 6, 6'.

In order that in attending to the device 9 both hands are at ones disposal the switch I in the device according to the invention is preferably so designed as to permit kneeor foot-control. In this case the construction of the switch may be such that upon releasing the control knob it resumes automatically its position of rest, for.

instance under the action of a spring 8 which is stressed upon parallel-connection of the input- "by the antennas I and 2 will preferably not be effected by controlling the bias of one or more discharge tubes, since the characteristic curve. of two corresponding tubes of the'two receivers never equalize each other exactly which may involve a deviation. Therefore in the direction finder according to the invention simultaneous control of the amplification of the two transmitting circuits takes place by variation of the transmission of the coupling quadrupole or coupling quadrupoles between two or more succeeding intermediate frequency amplifying stages, two succeeding stages in receiver 3 being designated by reference numerals l6 and I1 and two succeeding stages in receiver 4 being designated by numerals l8 and I9. This may, for instance, be effected by variation of a coupling condenser in one or more of the intermediate frequency bandpass filters of each of the receivers, the condenser in receiver 3 being designated by reference numeral l0 and that in receiver 4 by numeral II.

In the figure the reference numbers 20 and 21 designate the detectors and low-frequency amplifiers of the receivers 3 and 4 respectively. The variable coupling condensers are mechanically interconnected as is indicated by the dotted line l2. By a suitable arrangement and proportioning of the parts of the intermediate-frequency band-pass filters it can be achieved that upon variation of the coupling condenser the tuning of the circuits of the band-pass filters does not undergo variations.

What we claim is:

1. A direction finding system comprising two mutually perpendicular directional antennas, a pair of receivers, a cathode-ray indicator including first and second deflection means for deflecting the cathode ray in directions extending at right angles to one another, one of said antennas being coupled through one of said receivers to one of said deflection means and the other of said antennas being coupled through the other of said receivers to the other of said deflection niearls, a phase-shifting device interposed between one of said deflection means and the associated receiver, and switching means arranged to connect said two antennas in parallel relation.

-2. A direction finding system comprising two mutually perpendicular directional antennas, a pair of superheterodyne receivers including means for varying the amplification factor of both receivers simultaneously and to the same degree, a cathode-ray indicator including first and second deflection means for deflecting the cathode ray in directions extending at right angles to one another, one of said antennas being coupled through one of said receivers to one of said deflection means and the other of said antennas being coupled through the other of said receivers to the other of said deflection means, a phase shifting device interposed between one of said deflection means and the associated receiver, and switching means arranged to connect said two antennas in parallel relation.

A direction finding system comprising two mutually perpendicular directional antennas, a pair of superheterodyne receivers each provided with a multi-stage intermediate-frequency amplifier having an adjustable coupling condenser interposed between two successive stages to vary the amplification factor of the receiver, the adjustable condensers of said receivers being ganged together whereby the amplification factors of said receivers may be simultaneously varied to the same degree, a cathode-ray indicator including first and second deflection means for deflecting the ray in directions extending at right angles to one another, one of said antennas being coupled through one of said receivers to one of said deflection means and the other of said antennas being coupled through the other of said receivers to the other of said deflection means, a phase shifting device interposed between one of said deflection means and the associated receiver, and

switching means arranged to connect said two antennas in parallel relation.

HERMAN BERNARD RUDOLF BOOSMAN. CHRISTIAAN JAN DE LUSSANET DE Li SABLONIERE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,182,950 Steinhoif Dec. 12, 1939 2,407,649 Budenbom Sept. 17, 1946 FOREIGN PATENTS Number Country Date 553,618 Great Britain May 28, 1943 OTHER REFERENCES Proceedings of the I. R. E., Article by H. T. Friis, vol. 16, No. 95, pages 658-665, May 1928.

Electronics, Article by John P. Taylor, April 1939, pages 62-65. 

